U.S. Defense Secretary Ashton Carter says several members of the U.S.-led coalition fighting Islamic State (IS) militants in Iraq and Syria are doing "nothing at all" to help defeat the extremist group.

"Many of them are not doing enough, or are doing nothing at all," Carter told CNBC on the sidelines of the World Economic Forum in Davos, Switzerland, in a January 22 interview.

Carter did not single any country out, but his comments mark a departure from Washington's typical characterization of the 65-member coalition, whose slogan reads: "One mission, many nations."

He told Bloomberg TV in a separate interview that "we need others to carry their weight; there should be no free riders."

Carter told Iraqi Prime Minister Haider al-Abadi in a Friday meeting in Davos that the United States will intensify the fight against IS militants.

He met with defense officials from six nations -- mainly European -- this week, laying out broad plans for the campaign in the year ahead.